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Chapter 4
Themes
Key
LitCharts assigns a color and icon to each theme in The Beak of the Finch, which you can use to track the themes throughout the work.
Natural Selection and Evolution as Ongoing Processes
Nature and Humanity
Evolution, the Modern Era, and Nature’s “Resistance Movement”
The Interconnectedness of Species and Ecosystems
Hybridization and Specialization
Summary
Analysis
The Galápagos islands have suffered four years of drought, and there are now fewer Tribulus plants on the island than there used to be. Peter and Rosemary have to struggle and hunt in the dust to find them. And even those they do find aren’t fully eaten—this shows the Grants that the struggle for existence on Daphne Major is intensifying. During years with a lot of rain, the insect and plant populations are plentiful, the birds breed more prolifically, and their young prosper. But in years of extended drought—such as the years Boag spent on the island in 1976 and 1977—there are fewer birds that mate, fewer chicks that survive, and fewer insects and seeds for the finches that do make it to eat.
This passage illustrates how the ever-changing conditions on Daphne Major directly impact the finches’ capacity to survive. As nature changes around the finches, they must adapt to their surroundings or die. This illustrates how delicately, profoundly interconnected any given species is with its ecosystem. The smallest environmental shifts can have devastating impacts on the living organisms within that environment—and thus nature is in constant flux.
Themes
The drought of 1977 changed the behaviors of many different kinds of finches—some learned new ways of attacking the mericarps to extract fruit, while some began relying on Boag and his team’s camp for sustenance, drinking water and scavenging food from their tents. Some finches began eating the tails of the small lava lizards that ran around the island. Yet birds kept dying—and many skipped over their mating season.
This passage shows that changes in the finches’ environment directly and immediately impacted their behavior. The finches were learning to find new ways of securing food, stepping out of their territories and eating in ways they’d never eaten before in order to survive. A change in behavior is the first step in specialization—and the finches were, by this point, well on their way to being changed by their environment.
Themes
Boag went home dispirited, his data ruined. When he and his team returned in January of 1978, they found that just one in seven finches had made it through the drought—85% of fortis perished, 60% of the cactus finches died, and of the smallest ground finches, only one single bird survived. The biggest birds with the biggest beaks survived the drought the best—which meant that, though not in the way they hoped, Boag’s team had in fact seen natural selection in action, and they’d documented the most intense period of it on record. The tiniest variations in the birds’ characteristics had become a matter of life and death.
The smaller birds that were ill-suited to the drought’s demands—demands that they learn to attack the biggest, toughest seeds on the island or die—did not survive. But the birds who were already well-suited to the harsh drought conditions found a way to survive and pass on their advantageous traits. This passage illustrates how delicate life is—and how the smallest variations can end up making an enormous difference when an environment places selective pressures on the organisms within it.
Themes
Natural selection in and of itself, however, is not evolution—it is just a mechanism that leads to evolution. The finch watchers didn’t know whether the event they’d witnessed would lead to a real evolutionary change. But on January 9th of 1978, it rained more than 50 millimeters on Daphne Major. Within a week, the island was green and lush—and the finches began to seek new mates, since not a single coupled pair had survived the drought intact. Because more males than females had survived, the breeding season was skewed and only a small subsample of the largest males with the most intact plumage were able to mate. The new generation of finches on the island would be bigger and stronger than the last. Evolution was happening.
This passage shows how while selection had already acted on the finches, they hadn’t yet been pressured to evolve. But yet another environmental shift created conditions that would spur evolution. As the hardiest, most resilient birds mated with one another, they were passing on their favorable traits to their young—thus ensuring that future populations would be well-suited to handle tough, dry conditions. This shows that the beginnings of evolution can take place within just a couple of generations.
Themes
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In the 1980s, researchers with access to new kinds of technology further analyzed the data gathered during both the Galápagos droughts of the late 1970s and of the rainy season that followed. They found that selection was clearly, specifically favoring birds with the kind of beaks that would best allow them to twist and bite the mericarps of Tribulus plants apart. The finches on the island were forever “changed by their dead.”
In this passage, Weiner suggests that even the birds who are unable to survive in difficult conditions and end up dying off play a significant role in their relatives’ evolution. Death at the hands of natural selection isn’t meaningless; instead, Weiner suggests, it is full of great meaning. In a place like Daphne Major, no specimen, no matter their fate, is insignificant.
Themes
On Daphne Major, dead birds are commonplace, as opposed to other parts of the world where a dead bird is considered a shocking sight or even a bad omen. On this island, “the next generation builds on the ruins of the one before.” Evolution shows that there is meaning in death—and that there is, as William Shakespeare once said, “special providence in the fall of a sparrow.”
By invoking the words of William Shakespeare, Weiner is looking for the poetic or dramatic meaning in the “ruins” of a dead generation of birds. The author is awed by the interconnectedness of life on Daphne Major and the delicate nature of this particular ecosystem. He is trying to help his readers understand that evolution is a large and remarkable puzzle in which every part of a given ecosystem is a vital piece.
Themes
